A conventional rotary line switch, as shown in FIG. 1, comprises an upper cover 101, a lower cover 102 two contact strips 103 (only one shown) respectively fixed to the insides of both ends of the lower cover, a knob 104, a ratchet wheel 105 mounted on the knob with a bakelite washer 106 as a stop and set in between the contact strips, and a four-blade rotary connector 107 set on the ratchet-wheel to join the two contact strips indirectly. From the above, it is seen that the conventional rotary line switch is complex in construction and the knob and ratchet wheel are made individually. Idle running or poor transmission can occur when turning. The four-blade rotary connector is not only a waste of material, but also a cause of poor contact because it will shake after a certain period of use. Although a certain rotary line switches with integrally molded knob and ratchet, as shown in FIG. 2, have been developed to improve the transmission, they still employ four-blade rotary connectors. In addition, since rotary line switches which are mostly used for Christmas lamps or artist lamps are shipped with the upper cover and lower cover separated, the users must assemble them by themselves. But since the screw 108 used is a common one a journal and the stop bakelite washer must be installed, care must be taken when assembling. Otherwise the bakelite washer will be positioned incorrectly. To overcome the above-mentioned disadvantages, the present invention was developed.
A main object of this invention is to provide a rotary line switch of which the ratchet wheel and knob are integrally molded, so that no stop washer is needed and no transmission problem will occur.
Another object of this invention is to provide an improved rotary line switch which has a contact strip, a catch-contact strip and control constructed in such way that each 90 degrees rotation of the knob results in a tooth of the ratchet wheel pushing the end of the contact strip against the contact end of the catch-contact strip once.
Still another object of this invention is to provide an improved rotary line switch of which the screw has a journal which confines the control after it screws past the threaded part of the screw.